The present invention relates to the field of data storage systems, and in particular to data storage controllers of data storage systems providing data storage services to external requestors such as host computers.
Data storage controllers employ storage processors executing specialized programs for processing data storage commands from requestors such as host computer systems, as well as accessing data storage devices such as disk drives as necessary to write/read user data to/from the data storage devices as part of processing the data storage commands. A data storage processor may implement an in-memory cache, such as a block cache or file cache, for caching data read from or being written to the data storage devices. Such a cache is referred to herein as a “device cache” to distinguish it from other caches such as CPU caches. The storage processor preferentially writes/reads data to/from the device cache instead of a backing storage device when possible for improved performance in processing the data storage commands. The in-memory device cache may occupy the same physical memory used to store instructions and data of an operating system and other operating programs executing on the storage processor.